Exhaust gas emitted from an internal combustion engine, particularly a diesel engine, is a heterogeneous mixture that contains gaseous emissions such as carbon monoxide (CO), unburned hydrocarbons (HC) and oxides of nitrogen (NOx) as well as condensed phase materials (liquids and solids) that constitute particulate matter. Catalyst compositions typically disposed on catalyst supports or substrates may be provided in an internal combustion engine exhaust system to convert certain, or all of these exhaust constituents into non-regulated exhaust gas components.
Particulate filters (PF), remove the particulate matter from the exhaust gas. The particulate matter accumulates within the PF. The accumulated particulate matter causes an increase in exhaust system backpressure experienced by the engine. To address this increase, the PF is periodically cleaned, or regenerated. Regeneration of a PF in vehicle applications is typically automatic and is controlled by an engine or other controller based on signals generated by engine and/or exhaust system sensors. The regeneration event involves increasing the temperature of the PF to levels that are often above 600° C. in order to burn the accumulated particulates.
One method of generating the appropriate temperatures in the PF for regeneration includes delivering unburned HC to an oxidation catalyst device disposed upstream of the PF. The HC may be delivered by injecting fuel directly into the exhaust gas system or may be achieved by “over-fueling” or “late fueling” the engine resulting in unburned HC exiting the engine with the exhaust gas. The HC is oxidized in the oxidation catalyst device resulting in an exothermic reaction that raises the temperature of the exhaust gas. The heated exhaust gas travels downstream to the PF and burns the particulate accumulation. Such methods promote increased fuel consumption, which impacts overall fuel economy of the system.
Accordingly, it is desirable to provide systems and methods for regenerating a PF that will result in decreased fuel consumption.